Heat exchange device



y 1966 E. E. RHODES ETAL 3,250,325

HEAT EXCHANGE DEVICE Original Filed Feb. 19, 1963 INVENTORS BY 6m ATTORNEYS United States Patent 0 3,250,325 HEAT EXCHANGE DEVIQE Eugene E.Rhodes, Belleville, and Alvin M. Kurz, Oak

Park, Mich, assignors to Ford Motor Company, Dearhorn, Mich acorporation of Delaware Original application Feb. 19, 1963, Ser. No.259,547, now Patent No. 3,214,954, dated Nov. 2, 1965. Divided and thisapplication Apr. 2, 1965, Ser. No. 445,073

4 Claims. (Cl. 165-153) This is a division of application Serial No.259,547, filed February 19, 1963, now US. Patent 3,214,954. Thisinvention relates to heat exchange devices and to methods for themanufacture of the same. In particular, this invention relates to anovel heat exchange fin structure or spacer strip for use in a devicewherein heat exchange is effected between a liquid and a gas, as, forexample, in automobile radiators and heaters. Although the use of thefin structure here involved is not restricted to any particular field,it is especially adapted for use as a part of the main cooling system ofan engine and will be so referred to for the purpose of disclosing thenovel features embodied therein.

' Although details of construction may vary, an engine cooling radiatorordinarily includes an inlet tank and an outlet tank for suitableconnection with the water jacket of the engine, and a core or heatdissipating unit interposed between the two tanks for the travel ofwater in thin streams from one tank to the other through a number ofspaced passageways or water tubes of suitable heat exchange material.Between each pair of these water conduits fiows an air stream to take upor absorb heat carried by the water. A heat exchange fin structure andspacer element comprising a thin strip of a suitable metal or alloy,e.g. copper, brass, etc., is generally folded back and forth andinterposed between the water tubes for cooperation therewith to dividethe intervening space into a number of small air cells.

In this type of spacer strip the portion extending between folds ormajor corrugations will herein be referred to as the heat exchange fin,the fin proper or merely the fin.

It was early recognized that more eificient use could be made of the airflow between the water tubes if a greater proportion of the air streamis brought into direct contact with the metal of the spacer strip and/orthe walls of the water tubes. This led to the incorporation oftransverse serpentine corrugations to provide an undulating flow in theair passage through the individual cells. In other designs, openingshave been provided in the fin proper to allow air to flow from one cellinto another in its passage through the core. In modifications of thisdesign louvers have been employed adjacent to such openings to divertair through such openings.

The louvered fins heretofore employed exhibit certain undesirablecharacteristics. Some of these are inadequacies of the basic designwhile others result from the methods and tools employed to form theintended design.

Design weaknesses include improper positioning, alignment and shaping ofthe louvers employed. This can reduce the efficiency of the entirecooling system by misdirecting or failing to direct the air flow.Maximizing the cooling efficiency of the core results from maximizingthe wiping contact of the air on metal without undue impedance orresistance to flow. Too often in the past the value of laminar floweither has been overlooked or rejected in a misguided search for designsadapted to maximize turbulence. Furthermore, methods heretofore employedto form the design on the fin strip have resulted in uneven fin surfaceswhich impair the efficiency of the soldering process whereby the fin'ismade fast to the ad- 3,259,325 Patented May to, isles jacent watertubes. This results in both inadequate connections and the plugging ofthe air passages.

It is one object of this invention to provide an improved fin structurefor use in a heat exchange device as hereinbefore described which willincrease the heat absorption of an air stream passing through suchdevice while reducing obstructions to such flow which do not contributeto heat exchange eificiency.

It is another object of this invention to provide an improved finstructure that will reduce losses in heat exchange efiiciency thatresult from prolonged contact between air and the metal of such devicesafter a practical level of heat absorption has been reached.

Many other objects and advantages of this invention will be obvious tothose skilled in the art from the disclosure herein given:

In the drawings, wherein like reference characters indicate like orcorresponding parts:

FIGURE 1 is a partially completed front view of an automobile radiatorillustrating one use of the spacer strips or fin structures of thisinvention;

FIGURE 2 is a perspective view of a fin strip of this invention withportions thereof shown in the folded and unfolded state to illustratethe relationship of adjacent fins in the spacer strips of thisinvention; and

FIGURE 3 is a schematic view of two fins positioned on either side of anair cell and illustrating both the novel alignment and positioning ofthe fin louvers and representative paths of air particles passingtherethrough.

Referring to FIGURES 1 to 3, the radiator assembly, as will be readilyunderstood, includes a heat dissipating unit or core 11, having atopposite ends a top tank or inlet header 12, and a bottom tank or outletheader 13, adapted for connection, respectively, with the discharge andintake conduits of a cylinder block cooling jacket. For the flow ofcooling medium from one tank to the other the core'is made up of anumber of fiuid passageways or water tubes 14, spaced apartby fin strips15. The fin strip shown in the drawing is of folded or corrugatedoutline providing a series of fins 16 between folds or connectingmembers 17. The strips 15 therefore extend between adjacent walls to theadjoining tubes to divide the space into a number of relatively smallair cells or conduits l3. Ordinarily, the opposite edges or front andrear faces of the core assembly are dipped first in a fiux and then inmolten solder to seal the margins of the walls of the water tubes wherenecessary and to join the fin strips to the walls. It the passagewaysand tin strips are evenly formed so as to make possible continuouscontact from edge to edge, there will be an inward capillary flow ofsolder toward the center of the core, and a positive bond will resultthroughout substantially the entire depth of the core to insure the freeflow of heat into the fins.

Attention is now directed to the novel design of the fin proper andspecifically to FIGURES 2 and 3 of the drawings. Pin 16 is planar, i.e.a single plane and be passed. simultaneously through the entire lengthof both the longitudinal and transverse axes. For purposes ofconvenience such plane is hereinafter referred to as the central planeor base plane.

Provided in the planar fin 16 are groups of parallel transverse slots19, 24 and 26 through which air can pass from cell to cell. The slots 19and the adjacent louvers are formed by slitting the planar fin andturning the interpositioned strips out of the central plane. Thus, inthe embodiment shown the fin may be viewed as providing a pair of spacedapart louvered windows each of which provide a plurality of transverseopenings between louvers which are aligned in parallel relationship withrespect to the other louvers of the same window but inclined from thecentral plane of the fin at an equal and opposite angle from those ofthe next adjacent window. Although the fin of this embodiment providesonly two of such windows it is to be understood that one or moreadditional windows may be provided in other embodiments with the sameorder of louver reversal with respect to adjacent Windows.

The portion of the end supports adjacent the terminal slots 24 formouter diversion louvers 25 which are pivoted from their base so as toproject outward from one side of the central or fin plane. The edges ofcentral support 21 adjacent the central terminal slots 26 form inner orcentral diversion louvers 27. The term terminal herein is used withrespect to a given window, i.e. grouping of louvers and hence may or maynot mean terminal with respect to the entire fin. Louvers 27 are alsopivoted from their base so as to project from the central plane on theside opposite louvers 25. It will be noted that each of the outerdiversion louvers 25 is aligned in parallel relationship with thenearest inner or central diversion louver 27 and that louvers 25 and 27extend from opposite sides of the central or fin plane. While theprojecting edge of each of the outer diversion louvers 25 is inclinedtoward the nearest central support and in a two window fin toward thecenter thereof, the projecting edge of each of the inner or centraldiversion louvers 27 is inclined toward the nearest outer diversionlouver or away from the center of the fin. The remainder of the finprovides a central support 21, positioned between such windows, sidesupports 22 and end supports 23.

The strips between slots 19 and terminal slots 24 and 26 formintermediate louvers 28 each of which is turned out of the central planeby pivoting about its longitudinal axis so that louvers 28 extend out ofthe central plane in two opposing directions. However, it will be notedthat louvers 28 extend from the central plane for a lesser distance oneach side of the central plane than do the diversion louvers extendingfrom the corresponding side. In addition to being aligned in parallelrelationship with each other within each set, louvers 28 are also inparallel relationship with the diversion louvers 25 and 27 with whichthey are grouped.

Louvers 25, 27 and 28, except for the edges thereof where they arepivoted or twisted in relation to the supporting fin, are planarproviding a smooth, flat surface along essentially their entire lengthand breadth. In this embodiment central support member 21 between innerdiversion louvers 27 supported thereby is substantially equal in widthto each of the louvers 27. The major transverse measurement of suchlouvers is preferably as small as the method of manufacture andrequirements of structural strength will permit. Such louvers en massetherefore present to an air stream the largest practical wiping surfacecoupled with the minimum of impedance to air flow commensurate withmaximum heat exchange efficiency.

The diversion louvers 25 and 27 as aforementioned extend farther fromthe central plane than intermediate louvers 28. Terminal slots 24 arealso somewhat larger than intermediate slots 19. Slots 24, louvers 25,and louvers 27 being located in terminal and central positions are thusproperly shaped, sized and positioned to provide a primary diversioneffect upon an air stream entering one of the cells 18, escaping into anadjoining cell and eventually passing out of the radiator on the sidepposite from whence it entered. In cooperation with slots 19 and louvers28 the wiping air is passed along the louver faces from cell to celluntil the path of a representative particle of air is directed intocontact with central support 21 from whence it is diverted by the innerdiversion louver 27 that obstructs its original directional movementfrom cell to cell. This louver is aligned to divert the movement of theair particle toward a window of the adjoining fin opposite the windowthrough which it passed t before being diverted by louver 27 asillustrated in FIG- URE 3.

The number, size, alignment and positioning of the louvers as hereindisclosed provides an unexpected advance in the art making possible animportant reduction in the metal requirements of a given unit ashereinafter demonstrated. In the embodiment shown each fin is about 1.27inches in its longest measure and has a distance of about 1.17 inchesbetween the bend lines of the outer louvers 25. This embodimenttherefore provides a center support, two inner or central diversionlouvers, fourteen intermediate louvers and two outer diversion louversWithin a distance of 1.17 inches. In this type of fin there should be atleast 12, and preferably 14 or more, louvers per inch of fin, measuredalong the longitudinal axis of the fin proper. It will be understoodthat such measurement is along a line transverse to the longitudinalmeasurement of the fin strip of which the individual fins form a Bart.

This fin is thus designed to increase laminar flow and permits thecontact of a greater amount of unheated and lightly heated air to agreater area of unclogged heat exchange surface per unit of time or perair unit pass. The term clogging here relates to the phenomenon wherebya heat exchange surface is blanketed by a clinging film of air.

A device suitable for use in manufacturing the heat exchange finstructures or spacer strips of this invention and the method of itsoperation are disclosed in detail in the aforementioned patentapplication of which this application is a division. These disclosuresare incorporated herein by reference.

In the cutting and forming of the heat exchange fin structures or spacerstrips hereinbefore and hereinafter described transverse line contactupon the sheet material is continuously maintained from initiation ofsuch contact with opposing parts of a cutting and forming device untiltermination of the same. The resulting ironing effect not only producessmooth regular surfaces on the finished product in general but alsomakes possible the formation of straight or planar louvers, i.e.,louvers which except for their twisted ends are fiat sheets.

The advantages of the heat exchange fin structures of this inventionwill be more fully understood from the following operative exampleswhich should be considered as illustrative and not as limitations uponthe true scope of the invention as set forth in the claims.

Example I Fin strips of the configuration illustrated in FIGURE 2 andhaving the louvers thereof turned out of the planar base of the fin soas to'form an angle of 35 with such base were tested for coolingefficiency in an automobile radiator under operating conditionshereinafter described' The performance of the structure was comparedwith a commercially used slit fin structure of equal external dimensionsand total surface area. The comparison fin provided two terminallouvers, six intermediate louvers, and a central support bearing twocentral louvers. The: fins of the comparison fin strip prepared onconventional roll dies bearing essentially straight faced essentiallytriangular teeth were somewhat curved in general outline and ofgenerally uneven surface. All louvers of the comparison fin extendedfrom the main body of the fin for essentially the same distance incontrast to the configuration of the planar fins of this invention.

Tests were conducted usingthe fin strips of this invention and thecomparison fin strips in automobile radiators otherwise constructedalike. The tests were conducted on a S-mile circular track with anautomobile having an S-cylinder, 221 cubic inch displacement, gasolineengine. Tests were made at road speeds of 60, and miles per hour. Bothfin strips were tested using a 14 fin per inch ratio and the coolingetficiency of each recorded. The cooling efficiency of the planar fin ofthis invention proved to be higher than that of the control at eachspeed tested as measured by air-to-boil temperature. Airto-boiltemperature, a conventional measure of cooling systems, measures theambient air temperature at which the liquid medium, in this exampleWater, will boil.

These results were confirmed by other tests in which the vehicle wasconnected to a suitable dynamometer to simulate defined road grades bypulling a measured load. Tests were made at 30 miles per hour with a 7grade, at 45 miles per hour with a 5% grade and at 60 miles per hourwith a 4% grade. The fin of this invention again demonstratedsignificantly higher cooling eificiency than the comparison fin.

In both series of tests the degree of superiority demonstrated by thefin of this invention was most pronounced at the higher speeds, i.e. atthe more severe conditions.

Example 11 The testing procedure of Example I was repeated but with thefollowing difierences:

(1) The vehicle employed for the tests was equipped with an 8-cylinder,260 cubic inch displacement, gasoline engine.

(2) The fin of this invention was tested using a 14 fin per inch ratiowhile 15 fin per inch ratio was used for the comparison fin.

The fin of this invention demonstrated a higher cooling efiiciency thanthe comparison fin in the simulated grade tests.

Example III In standard Wind tunnel tests simulating the conditions ofExample I and using an S-cylinder, 260 cubic inch displacement gasolineengine, the cooling efiiciency of the fin of the invention was found tobe essentially equal to that of the comparison fin when a 15 fin perinch ratio was employed for the comparison fin and only a 13 fin perinch ratio for the fin of this invention.

Example IV The testing procedure of Example I was repeated but with thefollowing differences:

(1) The vehicle employed was equipped with an 8- cylinder, 352 cubicinch displacement, gasoline engine.

(2) The fin strip of this invention here used was a 1.27 inch copperstrip of the design shown in FIGURE 2 and was employed at the rate of 13fins per running inch.

(3) The comparison fin was a copper strip 1.95 inches wide and of thedesign used in Example II except that each fin included three louveredwindows separated by two internal supports similar to the centralsupport in the two window fins. The results of these tests are set forthin the following table:

TABLE I Thus, even with a surface area smaller than that of thecomparison fin by a ratio of about 16.5 to 23.4 the planar fin displayeda cooling etficiency substantially equal to the larger fin strip.

Having thus described the invention with particularity, it is obviousthat modifications can be made in the same without departing from thespirit and scope of the invention as set forth in the appended claims.

We claim:

1. In a heat exchange device having inlet means, outlet means, a coreincluding at least two conduits admitting of fluid flow therethrough andspaced apart to form an air passageway therebetween and a spacer elementpositioned between and in heat exchange relationship with said conduitswhich strip includes a plurality of fin elernents and connecting memberswhich together divide said passageway into a plurality of communicatingair cells, the improvement in said spacer element which comprises a finelement between each pair of said connecting members comprising a planarbase member; a plurality of spaced apart louvers integral with said basemember, arranged in spaced apart groups, and turned out of the plane ofsaid planar base member leaving at least one opening in said base memberadjacent each of said louvers; and between each pair of said spacedgroups a transverse member integral with said base member, each of saidspaced groups including a first diversion louver supported by the nextadjacent transverse member and extending out of said plane'on a firstside of said base member, a second diversion louver extending out ofsaid plane on a second side of said base member opposite said firstside, and a plurality of intermediate louvers between said firstdiversion louver and said second diversion louver, said intermediatelouvers extending through said plane and from said base member on saidfirst side for a distance less than said first diversion louver and onsaid second side for a distance less than said second diversion louver.

2. In a heat exchange device having inlet means, outlet means, a corecomprising a plurality of conduits communicating with said inlet meansand said outlet means, admitting of fluid fiow therethrough and spacedapart so that each adjacent pair thereof forms an air passagewaytherebetween and a spacer element positioned within each such passagewayand in heat exchange relationship with the conduits forming the same,said element including a plurality of fin elements integral with andpositioned between connecting members and dividing the passageway withinwhich the spacer element is positioned into a plurality of communicatingair cells, the improvement in said spacer element which comprises a finelement between each pair of said connecting members comprising aslitted planar base member; a plurality of spaced apart louvers integralwith said base member, arranged in spaced apart groups and pivoted outof the plane of said planar base member leaving at least one opening insaid base member adjacent each of said louvers; and between each pair ofsaid spaced groups a transverse planar member integral with said basemember, each of said spaced groups including a first diversion louversupported by the next adjacent transverse planar member and extendingout of said plane on a first side of said base member, a seconddiversion louver extending out of said plane on a second side of saidbase member opposite said first side, and a plurality of intermediatelouvers between said first diversion louver and said second diversionlouver, pivoted at two ends thereof from said base member so as toextend from said base member on said first side for a distance less thansaid first diversion louver and on said second side for a distance lessthan said second diversion louver, the major and central portions ofsaid intermediate louvers being planar and parallel to the said firstdiversion louver and said second diversion louver.

3. In a heat exchange device having inlet means, outlet means, a coreincluding at least two conduits admitting of fiuid flow therethrough andspaced apart to form an air passageway therebetween and a spacer elementpositioned between and in heat exchange relationship with said conduitswhich strip includes a plurality of fin elements and connecting memberswhich together divide said passageway into a plurality of communicatingair cells, the improvement in said spacer element which comprises a finelement between each pair of said connecting members comprising a fiatbase member the longitudinal and major transverse axes of which extendthrough a base plane; a plurality of spaced louvers integral with saidbase member, pivoted from said base member to extend out of said baseplane and leave at least one opening in said base member adjacent eachof said louvers, said louvers being arranged in a first group of louversand a second group of louvers spaced apart therefrom; and positionedbetween the louver groups a transverse planar member integral with saidbase member, each group of said louvers including a first diversionlouver pivoted along one side thereof from said transverse planar memberand extending out of said plane on a first side of said base member, asecond diversion louver pivoted along one side thereof from said basemember and extending out of said plane on a second side of said basemember opposite said first side, and a plurality of intermediate louversbetween said first diversion louver and said second diversion louver andpivoted at two ends thereof from said base member so as to extend fromsaid base member on said first side for a distance less than said firstdiversion louver and on said second side for a distance less than saidsecond diversion louver, said first group of louvers bein'g aligned forthe major part of their respective lengths in parallel relationship witheach other and forming a constant acute angle with said base member onthe side of their respective extensions, said second group of louversbeing aligned for the major part of their respective lengths in parallelrelationship with each other and forming a constant acute angle withsaid base member on the side of their respective extensions which isequal and opposite to the angle formed by louvers of said first group.

4. In a heat exchange device having inlet means, outlet means, a coreincluding at least two conduits admitting of fluid flow therethrough andspaced apart to form an air passageway therebetween and a spacer elementpositioned between and in heat exchange relationship with said conduitswhich strip includes a plurality of fin elements and connecting memberswhich together divide said passageway into a plurality of communicatingair cells, the improvement in said spacer element which comprises a finelement between each pair of said connecting members comprising a planarbase member; a plurality of spaced apart louvers integral with said basemember, arranged in spaced apart groups, and turned out of the plane ofsaid planar base member leaving at least one opening in said base memberadjacent each of said louvers; and between each pair of said spacedgroups a transverse planar member integral with said base member, eachof said spaced groups including a first diversion louver supported bythe next adjacent transverse member and extending out of said plane on afirst side of said base member, a second diversion louver extending outof said plane on a second side of said base member opposite said firstside, and a plurality of intermediate louvers between said firstdiversion louver and said second diversion louver, said intermediatelouvers extending through said plane and from said base member on saidfirst side for a distance less than said first diversion louver and onsaid second side for a distance less than said second diversion louver,said fin element having a minimum of 12 louvers per running inch asmeasured along the longitudinal axis thereof, said louvers each formingwith said base member an angle of about 25 to about References Cited bythe Examiner UNITED STATES PATENTS 2,063,757 12/1936 Saunders -1532,133,502 10/1938 Emmons 165-153 2,252,211 8/1941 Seemiller 165-1522,647,731 8/1953 Ludlow 165-152 X 2,703,226 1/1955 Simpelaar 1651532,838,830 6/1958 Huggins 29-1573 6,003,749 10/1961 Morse 165-1523,136,038 6/1964 Huggins et al. 29-1573 ROBERT A. OLEARY, PrimaryExaminer. FREDERICK L. MATTE SON, JR., Examiner. M. A. ANTONAKAS,Assistant Examiner.

1. IN A HEAT EXCHANGER DEVICE HAVING INLET MEANS, OUTLET MEANS, A COREINCLUDING AT LEAST TWO CONDUITS ADMITTING OF FLUID FLOW THERETHROUGH ANDSPACED APART TO FORM AN AIR PASSAGEWAY THEREBETWEEN AND A SPACER ELEMENTPOSITIONED BETWEEN AND IN HEAT EXCHANGE RELATIONSHIP WITH SAID CONDUITSWHICH STRIP INCLUDES A PLURALITY OF FIN ELEMENTS AND CONNECTING MEMBERSWHICH TOGETHER DIVIDE SAID PASSAGEWAY INTO A PLURALITY OF COMMUNICATINGAIR CELLS, THE IMPROVEMENT IN SAID SPACER ELEMENT WHICH COMPRISES A FINELEMENT BETWEEN EACH PAIR OF OF SAID CONNECTING MEMBERS COMPRISING APLANAR BASE MEMBER; A PLURALITY OF SPACED APART LOUVERS INTEGRAL WITHSAID BASE MEMBER, ARRANGED IN SPACED APART GROUPS, AND TURNED OUT OF THEPLANE OF SAID PLANAR BASAE MEMBER LEAVING AT LEAST ONE OPENING IN SAIDBASE MEMBER ADJACENT EACH OF SAID LOUVERS; AND BETWEEN EACH PAIR OF SAIDSPACED GROUPS A TRANSVERSE MEMBER INTEGRAL WITH SAID BASE MEMBER, EACHOF SAID SPACED GROUPS INCLUDING A FIRST DIVERSION LOUVER SUPPORTED BYTHE NEXT ADJACENT TRANSVERSE MEMBER AND EXTENDING OUT OF SAID PLANE ON AFIRST SIDE OF SAID BASE MEMBER, A SECOND DIVERSION LOUVER EXTENDING OUTOF SAID PLANE ON A SECOND SIDE OF SAID BAASE MEMBER OPPOSITE SAID FIRSTSIDE, AND A PLURALITY OF INTERMEDIATE LOUVERS BETWEEN SAID FIRSTDIVERSION LOUVER AND SAID SECOND DIVERSION LOUVER, SAID INTERMEDIATELOUVERS EXTENDING THROUGH SAID PLANE AND FROM SAID BASE MEMBER ON SAIDFIRST SIDE FOR A DISTANCE LESS THAN SAID FIRST DIVERSION LOUVER AND ONSAID SECOND SIDE FOR A DISTANCE LESS THAN SAID SECOND DIVERSION LOUVER.